When travelling, it's generally smart to pack in preparation for rain or any other conditions that may arise. The rainfall in Johor Bahru is roughly less than Exeter. You can assume this to be the case over the next 0 days.
You can imagine temperatures to be in the 33 °C range in April. The weather in Exeter is generally colder than Johor Bahru's. As flight availability is subject to become more limited as peak season approaches it is ideal to book in a timely manner.